摘要
In combination with petrological data, SHRIMP and LA-ICPMS U-Pb geochronology on two HP granulite samples in the Songshugou area of the North Qinling orogen yield ages of (504±7) Ma and (506±3) Ma, respectively, representing the time of high pressure granulite metamorphism. This implies that HP granulite-facies conditions in high pressure granulite and eclogite facies conditions in eclogites developed at the same time but they formed in different thermal environments. The results suggest that the North Qinling orogen experienced an Early Ordovician subduction and crustal thickening, followed by an Early Silurian widespread Barrovian-type metamorphic event as observed in many collisional orogen.